I. Introduction
Humidity and temperature sensing is of significant interest in applications, such as environment monitoring [1], personal healthcare [2], [3], [4], [5], electronic skin (e-Skin) [6], [7], [8], food packaging [9], [10], [11], and agriculture [12], [13]. The regular and continuous monitoring of these parameters is important in the above applications. For example, most of greenhouse plants/crops require relative humidity in/around the range of 40%–80% [14], [15], [16] and optimal air temperatures in/around the range of 17 °C–27 °C [13], [15], [17]. This means that it is important to maintain the desired levels of humidity and temperature to ensure high growth rates of greenhouse crops/plants. This need for humidity and temperature measurements calls for cost-effective sensors, and as a result, a wide variety (e.g., capacitive, resistive) of temperature and humidity sensors have been explored [6], [7], [18], [19], [20], [21], [23]. However, complex synthesis, nonflexible form factors, and cost-ineffective fabrication hinder their widespread use. In this regard, printed sensors on flexible substrates offer an attractive route for flexible electronics applications [24], [25], [26]. The capability to choose the printing ink, substrate, and the flexibility of designing the electrode with desired pattern offers numerous opportunities to enhance the performance of these sensors. Furthermore, resource-efficient printing could improve the commercial viability of these sensors [27].